Cracked block....recommendations?

-
66durgederp

66durgederp

"pull hard, itll come easy"
Joined
Aug 31, 2012
Messages
554
Reaction score
70
Location
Zoo montana
When I did my 318 swap in my 66 it always had a mystery antifreeze "weep" it would go through half a gallon of coolant about every 1 1/2 to 2 weeks. figured it was the block drain plug threads on the passengers side, gooped em up, problem seemed to go away. Then I installed an aluminum radiator and flushed the hell out of the cooling system, problem came back. It didnt help that i slapped a fresh coat of paint on it as well. Its been like this for a long time evidently, because for me, its always seeped, and i know the guy whom i bought it from had the same problem. now that its sat for 5+ months the paint has flaked away and its pretty obvious now. Its cracked on the passenger side, perfectly centered between the front and middle freeze plugs, about 3/4 of an inch above the block drain plug. Really bums me out because this thing is so clean and runs so well, uses no oil, and is peppy as hell. I know a cracked block is nothing to putz around with, so im after some suggestions. Im thinking ill run this beast until i can locate a new engine...hopefully. luckily i have located a .030 over 318 shortblock with flat-tops, unknown cam (ill probably swap it out reguardless) Im going to go check out this monster to see how deep the slugs are in the hole and go from there. Anywhore, had anyone out there had ANY luck nickel-rodding a crack? i contemplated block sealer for about 2 seconds then slapped myself...cause that stuff is no bueno, and im not for ruining my brand new 200+ dollar radiator...so, save it? nickel rod it? block seal it? (*shiver*) run it? sell it for a derby motor?
 
I had a busted block 383 magnum in my Charger for years . It was split up in the lifter valley . I had a professional weld it up , and even 10 years later , I never had a bit of trouble with it . Its still sitting in my garage waiting for another B-body to make it a nice new home .
 
It can be stitch welded but you would have to pull it out to do that. Just find someone good and do it right and only once.
 
It can be welded, but it is not cheap. I would be looking for a new good block and transferring everything over. To get by, drain the block and clean it well and try JB weld on the crack. Maybe drill the ends of the crack to keep it from traveling. There used to be a company in MD that sold prepped blocks..Block in a Bag.
 
Just have it welded by a professionally who does cast. Just make sure you talk to people that have used him. It is not that much money to do. you just want somebody who knows how's what there doing. We have a great guy over here that does unbelievable work with cast.
 
Have to use nickle welding rods on cast iron, I have seen someone actually braze up a nice big crack in a block, now if that held up I dont know LOL.
 
i seen this crazy repair before, where a guy drilled and tapped along the crack and filled it with 3/8 bolts, started at one end and worked along the crack, each new hole would cut into the last bolt edge a bit.. looks crzy as hell , but it worked,. i think i read it in a hotrod magazine once too they did a cylinder head that way,
 
68gtx said:
i seen this crazy repair before, where a guy drilled and tapped along the crack and filled it with 3/8 bolts, started at one end and worked along the crack, each new hole would cut into the last bolt edge a bit.. looks crzy as hell , but it worked,. i think i read it in a hotrod magazine once too they did a cylinder head that way,
Click to expand...

This is what I was refering to in my above post. I call it stitch welding, though the ones I've seen done use a much smaller thread than 3/8's.
 
stic tite radiator repair from speedway motors probably pull the exhaust manifold for some clearance to work on the block right in the car
 
If it's just a small crack/porosity, and not structurally compromised, just braze it up. The brazing will wick down into the crack and seal it up.
 
Years ago a guy I worked with bought a cadillac cheap because of the same crack. The block had frozen and cracked from one freeze plug to the next. We flushed all the coolant out of the system, poured a bottle of barsleak in it and ran it. A wide stream of water slowly became several tiny leaks before completely stopped. He also put a weak system cap on it ( 7 lbs ). As far as I know it never leaked again.
I think the key to success with those type products is the flush. It isn't going to bond where antifeeze is.
 
Drain it down below the crack then grind it shiny on the crack and jb weld
It won't leak again as long as you get the area clean
 
cudascott said:
Drain it down below the crack then grind it shiny on the crack and jb weld
It won't leak again as long as you get the area clean
Click to expand...

I agree...I did a 318 back in the mid 80's like that and the engine ran another 100,000 miles. after grinding i would spray the crack with brake cleaner and let it dry for an hour or 2 before jb welding it. I did the same repair on an old 70 John Deere diesel a few years ago and it still doesn't leak.
 
thank you all kindly, since this crack is as straight as straight can possibly get, and so perfectly centered from freeze plug to freeze plug, is the integrity of the block compromised especially since the motor mount is right next to it? should i worry about this spreading over time with heat cylcles and vibration?
 
when you have it fixed the right way, they will drill a hole a the end of the crack to stop it from spreading. yes it will keep spreading. how fast nobody knows. its one of those things. may take years or spread fast.
i would not but anything in the cooling system unless you do not care about your cooling system.
how important is the block?
 
Im voting the jb weld on a 318 You can get another 318 or 360 block for 100 bucks so jb and enjoy.
 
if the crack spreading is a concern drill a small hole at each end. That will stop the crack in its tracks. (sorta rhyme intended) lol
 
good points...the block isnt that important. I just dont want to be cruising around and KABOOM!!!! BILLY MAYS HERE!!!! :D i dont think ive been specific on this crack, it starts IN the passenger front freeze plug bore, and ends IN the middle freeze plug bore.....its cracked perfectly centered from one to the other, so i guess i already have my holes to keep it from spreading....Ive located a .030 over shortblock, forged aluminum pistons, factory rods, .010/.010 under crank...if the slugs arent any more than .020 in the hole then im thinking ill freshen up the 360 heads currently on my engine, and run em, should be roughly 9:1 static. just another project to add to my ever growing "to-do" list...
 
The best way is drilling each end, to stop the crack. Then angle grind a vee in it. Then heat it with a torch, then high nickel, beat it with a slag pick hammer, to relieve stress. Re-heat, again, easy, so it cools down slowly.several smaller steps.
 
not a mopar,..but got a sbc cracked from freaze plug almost to next freaze plug,....drilled end of crack,ground a v threw the crack,wielded with high nickle rod,..cooled slow 12 to 15 years ago an still holding water now in my dirt track car...id try the j-b wield an run it till she wares out long as it holds,..seen cracked detroit diesel run 250,000 miles repaired with j-b!
 
grind clean and JB it, not the fast stuff but the original. Done deal. Already stopped cracking years ago....Its not going to burst, if at all it will start to weep again. And the motor mount is not outside the water jacket in the bock wall, but is supported in the back too as I recall. But really, a std bore 318 can be had almost anywhere for cheap.
 
agreed pishta, ive located a fresh mid 70s .030 over 318, forged aluminum flat top pistons, .010/.010 cast crank, factory rods. waiting for measurments on how far in the hole @ TDC the pistons are, and i figure i can have my current heads (360 heads, 1.88 int) and intake milled accordingly. shooting for the 9.5:1 compresion range. leaning towards a comp 20-212-2 hydraulic flat tappet high energy cam, 268 degree duration, .454 lift int/exh, 110 lobe spread. so with that, brand new slugs, decent rings, (still debating on that, recommendations are appreciated) new bearings, freshened up 360 heads, minor home porting job, valve jobbed and milled accordingly, comp 901-16 springs to compliment the cam, maybe some custom pushrods if needed, 822-16 lifters, dual roller timing chain, high volume pump, re-use current windage tray and tin-work. I think it would be a decent streetable motor with some extra snort to make the more-door move. also, keeping the build under 1000. working at a parts house really helps....i doubt the average joe could keep the cost lower, but im lucky i spose. ill just run this current mill until im ready to get the new one swapped. once again, thank you gents for your input.
 
JB WELD!!

During the summer my buddy got a running 350 with nice cam and intake on it for $500, came with a camaro too. Anyway we did a nice burnout then pulled the motor. he was happy that it seemed like a great running motor supposedly recently rebuilt. Then we saw the block had a nice crack in it where coolant must have froze. my buddy was real bummed. I was like its just a stock 350 bottom end slap some jb weld on it and drive it! so we did. Its only been maybe 6-7 months but he drives this thing HARD. 6000 rpm most of the time hes behind the wheel. He has been through 3 sets of rear tires since the engine went in, 1 t5 trans as well. It also dropped a valve through a piston, put a new piston in and beat it harder. No issues so far with the jb weld.

I would clean it up really good, apply a generous amount of jb weld, give it plenty of time to cure. then drive it and take your sweet time building the other motor.
 
You must log in or register to reply here.
-

Back
Top